Based on mine in the deep buried depth, high gas content, coal seam gas drainage with low permeability problem, in order to improve the permeability of coal seams and accelerate the gas flow, coal body is damaged by hydraulic fracturing to make gap in coal seams to flow the gas and improve the plasticity of coal through water injection. In this paper, the RFPA2D-Flow numerical simulation method is used to simulate and analyze the stress change of coal body around the borehole, the change of coal body displacement and the distribution of head pressure around the borehole. The results showed that under the condition without free hole, when the injection pressure is gradually increased, coal cracks gradually become larger; with free hole, when the injection pressure increases gradually, borehole pressure relief range also increases gradually.